Shear plate and cutter assembly for rotary type dry shaver



J. BRUECKER Feb. 6, 1962 SHEAR PLATE AND CUTTER ASSEMBLY FOR ROTARY TYPE DRY SHAVER 2 Sheets-Sheet 1 Filed June 29, 1960 J. BRUECKER Feb. 6, 1962 SHEAR PLATE AND CUTTER ASSEMBLY FOR ROTARY TYPE DRY SHAVER 2 Sheets-Sheet 2 Filed June 29, 1960 illm 3,019 525 SHEAR PLATE AND CUTTER ASSEMBLY FOR RQTARY TYPE DRY SHAVER John Bruecker, 1100 N. Verdugo Road, Glendale, Calif. Filed June 29, 196i Ser. No. 39,591 5 Claims. (Cl. 30-43) The present invention relates to improvements in mechanical razors, commonly referred to as dry shavers, and which are usually, but not necessarily, electricallypowered. The invention is specifically concerned with a novel shaving head for such shavers and which embodies a novel form of shear plate and cooperating cutter.

Classified as to their basic mode of operation, with but few exceptions, electrically-powered dry shavers have, since their advent upon the market, been of three types, namely, the oscillatory type, the reciprocating type, and the rotary type, these designations being based upon the kind of motion imparted to the cutter element. The pres ent invention is concerned essentially with dry shavers of the rotary type. As the designation suggests in the rotary type of dry shaver, the cutter may have either a straight or a curved cutting edge which sweeps in circumferential fashion around the inside face of a conformably shaped shear plate.

Insofar as I am aware, present-day dry shavers of the rotary type are possessed of shear plates which are flat or which possess a limited degree of curvature, which is to say, that they deviate from true flatness only by virtue of the fact that they are fashioned on a long radius of curvature. Similarly, the cutters associated therewith have cutting edges which likewise are either linearly straight or which are curved on a long radius. With such shavers, the shaving operation is predicated upon holding the instrument so that the shear plate lies fiat, or nearly flat, against the skin of the user and very little tilting of the instrument about its longitudinal axis relative to the plane of the skin is permissible. It follows, therefore, that shaving instruments of this character must be used with a considerable degree of skill and care if an effective shaving action is to be attained.

The logical way to overcome the above-noted limitation which is attendant upon the construction and use of dry shavers of the rotary type would be to decrease the radius of curvature of the shear plate, but when this is done, an article results which is too small to be practical in that the shaving area is materially decreased and also peripheral cutter speed is appreciably reduced. Furthermore, due to the small size of the shear plate, the design of a suitable cutter and its drivi g mechanism presents a watchmakers problem.

The present invention involves a different approach to the problem in that it contemplates the provision of a novel form of circular shear plate where a large extent of peripheral sweep of the cutter is maintained, while at the same time the shear plate, in the peripheral regions thereof, affords the necessary degree of curvature for proper presentation of the edges of the shearing perforations to the skin at widely difierent shaving angles. Briefly, this sharp curvature in the peripheral regions of the shear plate is accomplished by the provision of a lateral concavo-convex torus which extends around the peripheral regions of the otherwise fiat shear plate and which is provided with a series of inner shear perfora tions and a series of outer shear perforations, i.e., with shear perforations on opposite sides of the torus crest. A generally circular disk-like cutter element having an arcuate cutting edge commensurate in extent and curvature to the arcuate extent and curvature of the convex face of the torus is adapted to sweep around the inside of the torus in circumferential fashion. The radius of curvature of the torus measured from inside the torus, its

'atent Ofiiice 3,l9,525 Patented Feb. 6, 1962 mean diameter measured from the center of the circular shear plate, and its arcuate or offset extent, are correlated so that the torus presents a relatively large shearing area. The large radius of curvature of the torus enables the use of a cutter of commensurately large diameter so that machining and other cutter manufacturing operations are simplified; the large mean diameter of the torus affords an appreciable cutter sweep for each cutter revolution; and the large oifset arcuate extent of the torus serves to concentrate the manual pressure which is applied to the instrument as a whole against localized areas of the skin so that effective shearing may be attained with what may be termed a light touch.

Numerous other advantages accrue from the use of a shear plate having such a torus configuration, one of these being the fact that a single pass of the instrument across the face of the user in any direction whatsoever result in the application of two leading shearing areas of the torus to the skin, namely, a primary outside or foremost shearing area on the outside of the torus crest, and a secondary shearing area on the inside of the torus crest which trails the first shearing area 'but which leads the extreme trailing area of the torus on the outside thereof.

The provision of a dry shaver having a shear plate and cutter construction of the character briefly outlined above being among the principal objects of the invention, a further object is to provide a cutter construction having novel means whereby the cutter element proper is effectively counterbalanced against the action of centrifugal force which otherwise would tend to create undue shearing pressure against that portion of the concave side of the shear plate torus which lies on the outer side of the torus crest.

A similar and related object of the invention is to provide a cutter construction having novel means whereby the cutter is floatingly carried at the end of the driving arm on which it is mounted to the end that it will be self-seating against the inside surface of the torus within which it moves, While at the same time the circular cutting edge thereof is maintained parallel to the torus axis so that no portion of the cutting edge will move out of shearing engagement with the inside or concave face of the torus.

Numerous other objects and advantages of the invention will readily suggest themselves as the following description ensues.

In the accompanying two sheets of drawings forming a part of this specification, one illustrative embodiment of the invention has been shown.

In these drawings:

FIG. 1 is a fragmentary sectional view taken substantially centrally and longitudinally through one form of a shaving head constructed in accordance with the principles of the present invention;

FIG. 2 is an enlarged fragmentary detail side elevational view of a portion of the structure shown in FIG. 1;

FIG. 3 is a top FIG. 1;

FIG. 4 is a sectional view taken substantially along the line 44 of FIG. 1; and

FIG. 5 is an enlarged fragmentary quarter-section top plan view similar to FIG. 1 illustrating a slightly modified form of the invention.

Referring now to the drawings in detail, and in particular to FIG. 1, only those portions of a complete shaving implement which are necessary to an understanding of the present invention have been disclosed. The disclosed portions include a shaving head 20 and a limited portion 22 of the shaver casing which encloses the motor by means of which the head is actuated. The casplan view of the structure shown in ing 22 is provided with an upstanding annular flange 24 which threadedly receives thereover the lower rim portion of the cylindrical side wall or shell 26 of the head. The outer circular rim 28 of the shell 26 is closed by a generally circular preforated shear plate 30, the shape and design of which constitutes one of the principal features of the present invention. The marginal region of the shear plate 30 is adapted to be removably clamped to the rim of the shell by means of a clamping band 32 having an inturned clamping flange 34 which overlies a marginal seating flange '36 on such marginal region of the plate and which serves to clamp the seating flange against a bevelled surface 38 on the shell rim. Bayonet slot connections 39 serve removably to retain the band 32 in operative position on the shell 26.

The circular shear plate is provided with a relatively large fiat central hub portion 40 and a coplanar rim 42, the extreme marginal region of which is turned downwardly to provide the previously mentioned seating flange 36. Between the flat central hub portion 40 and the fiat rim 42, there is formed a lateral concavoconvex torus 50, the cross sectional arcuate extent of which, in the illustrated form of the invention, is approximately 90 or one-quarter of a circle.

The torus has formed therein two parallel concentric circular rows of elongated shearing slots including an inner row of slots 52 and an outer row of slots 54 (FIG. 3). The slots 52 and 54 are arranged in radially disposed pairs relatively to the shear plate 30 and the axes of the siots of each pair are inclined relatively to each other at an obtuse angle. The two rows of slots are spaced apart a slight distance and thus provide a narrow band 56 therebetween which lies upon the crest of the torus. The band or torus crest 56 is shown in FIGS. 1 and 3 as being imperforate, but in the modified form of shear plate shown in FIG. 5, it is provided with a series of small circular holes 57a.

The slots 52 and 54 extend well into the marginal regions of the torus St) on both the inner and outer side of the latter and adjacent slots in each row define therebetween a series of narrow ribbons 58. The manner in which the shear plate 30 is formed constitutes no part of the present invention. However, it is deemed pertinent to state that the shear plate may be formed from a fiat circular blank by prepunching the various slots therein in the approximate region of the torus and, thereafter, effecting a circumferential shift of the band 56 relative to the hub 40 and marginal rim 42 while at the same time forcing the band 56 out of the plane of the blank and into coincidence with the outline of the torus crest, after which the intervening ribbons 58 are shaped and caused to move into the outline of the remainder of the torus. By such a method, it is possible to create the torus in the blank by merely shifting the position of the. band 56 and ribbons 58 without stretching the metal of the blank. For a full disclosure of such a method, reference may be had to my copending application Serial No. 39,592, filed on June 29, 1960, and entitled, Method of and Apparatus for Forming Perforated Shear Plates for Dry Shavers of the Rotary Type.

The shear plate 30 is adapted to cooperate with a series of three cutters 60, each having a generally circular cutting edge 62 adapted to sweep around the torus 50 interiorly thereof as in circumferential fashion, as best seen in FIG. 1. Each cutter 6a is of cup-shape, frusto conical design and includes a circular attachment base 64, frusto conical side walls 66 and a circular rim 63 affording the previously mentioned cutting edge 62.

The cutting edge 62 is of saw-tooth design, as best seen in FIG. 5, the teeth thereof existing by virtue of the provision of alternate troughs and crests in the rim 68, these troughs and crests being undercut or cut back on an incline in accordance with the principles of cutter design shown and described in my earlier filed application Serial 4%- No. 27,688, filed on May 9, 1960, and entitled Shaving Head and Cutter Therefor.

The cutters 60 are floatingly carried in a manner that will be made clear presently at the outer ends of a series of radial arms 70 provided on a hub 72 carried at the upper end of a drive shaft 74. The hub 72 is slotted as at 76 to receive a cross pin 78 by means of which the hub is driven from the drive shaft 74 while at the same time having a limited degree of vertical sliding movement on the shaft. A spring 80 bears. at its lower end against a collar 82 secured as at 84 to the shaft 74 and at its upper end against the underneath end face 85 of the hub 72 and serves normally to urge the hub upwardly and thus maintain shearing pressure of the various cutters 60 against the inside or concave face of the torus 50. The shaft 74 is adapted to be rotated in one direction by means of a suitable motor (not shown) and operatively mounted within the confines of the shaver casing 22.

As best seen in FIGS. 1 and 4, the floating connection for each of the three cutters 6i) at the ends of the radial arms 70 includes a yoke 10ft loosely pivoted medially of its ends on a shouldered pin 162 threadedly received in an enlargement 104- on the end of the arm 70. The upper end of the yoke has rivoted thereto as at 165 the cutter 60, the connection being a friction-tight connection with the base 64 fitting flush against the flat forward face of the yoke so that turning of the cutter on the rivet 105 normally is prevented, while at the same time a forced turning of the cutter may be effected when the head 20 is disassembled so that a fresh cutting edge may be presented to the inside concave face of the torus 50. The lower portion 106 of the yoke 169 constitutes a counterbalancing mass for the cutter 60 so that upon revolution of the cutter around the inside of the torus circumferentially will effect even distribution of shearing forces against the torus as a whole.

In the operation of the shaving head 20, upon rotation of the shaft 74, the hub 72, yokes and cutters 60 will turn bodily as a unit and the cutters will be caused to sweep around the inside face of the torus 50, each with the cutting edge 62 thereof in intimate shearing contact with the latter. The saw-tooth cutting edge 62 will encounter the parallel sides of the elongated shear perforations or slots 52 and 54 at an angle to thus improve the shearing action. The plane of the circular rim 6% will be maintained normal to the transverse torus are by virtue of the enlargement 104 which acts as a reaction backing for the yoke 100. The moment of centrifugal force acting on the counterweight 106 is substantially equal to the moment of centrifugal force acting upon the cutter 60 and, thus, regardless of cutter speed, equal distribution of shearing force against the concave side of the torus will at all times be maintained.

The shearing head 2th: fragmentarily shown in FIG. 5, is similar to that shown in FIGS. 1 to 4, inclusive, and previously described. Therefore, to avoid needless repetition of description, similar characters of reference to which the suffix a have been applied appear in FIG. 5

to designate corresponding parts. The cutters 60a and.

their mountings remain precisely the same as the cutters 6(3 and their mountings. The shear plate 50:: is of slightly different design albeit of the same overall configuration. The elongated shear slots 52a and 54a, instead of being inclined toward each other counter to the direction of; travel of the cutters, are inclined toward each other in the direction of travel of the cutters. Also, the circular band 56a at the crest of the torus 5th is provided with thel previously mentioned series of small shear holes 5741.; The operation of the shaving head does not differ appreciably in function from the shearing head 20, since the cutting edges 62a of the cutters 6t} encounter the parallel sides of the various shear slots at an angle for more efficient cutting. 1

While the invention is susceptible of various modifica 3 lions and alternative constructions, there has been shown in the drawings and described herein the preferred embodiments. It is to be understood, however, that it is not intended thereby to limit the invention to the forms dis closed, but it is intended to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

1. In a shearing head for dry shavers of the rotary type, in combination, a generally circular shear plate provided with a lateral concavo-convex torus, said torus being formed with a first row of elongated spaced slots having parallel shearing edges and disposed on one side of the torus crest, and a second row of similar slots on the other side of the torus crest, the longitudinal axes of the slots of each row being parallel, the slots of the two rows being arranged in radially aligned pairs with the longitudinal axes of the slots of each pair extending at an obtuse angle to each other, a cutter movably mounted for circumferential sweeping movement around the inside concave face of said torus and having an arcuate cutting edge shaped conformably to the cross sectional curvature of said concave face, and means for effecting revolution of said outter about the longitudinal axis of the torus.

2. In a shearing head for dry shavers of the rotary type,

the combination set forth in claim 1 wherein the torus crest is formed with a series of closely spaced small shearing holes therein.

3. In a shearing head for dry shavers of the rotary type, in combination, a generally circular shear plate provided with a lateral concave-convex toms, there being a series of shear perforations in said torus, a cutter movabh mounted for circumferential sweeping movement around the inside concave face of said torus and having an arouate cutting edge shaped conformably to the cross sectional curvature of t e said concave face, a rotary drive shaft concentric with the longitudinal axis of the torus, a hub slidable axially on said drive shaft, means providing a driving connectionhetween the drive shaft and hub, a radial arm on said hub, a yoke pivoted intermediate its ends to the outer end of said radial arm, said cutter being mounted on one end of said yoke, and counterbalancing means for the cutter on the other end of the yoke.

4. In a shearing head for dry shavers of the rotary type, the combination set forth in claim 3 and including, additionally, an enlargement on said radial arm, and slidingly interengaging surfaces on said enlargement and yoke for assimilating the reaction thrust of the cutter and thus preventing tilting thereof relative to the shear plate.

5. In a shearing head for dry shavers of the rotary type, the combination set forth in claim 3 and wherein said yoke is loosely pivoted to the outer end of said radial arm to permit freedom of floating movement of the cutter against the inside concave face of the torus.

References Cited in the file of this patent UNITED STATES PATENTS 2,026,630 Harris Ian. 7, 1936 2,134,609 Hay Oct. 25, 1938 2,212,624 Testi Aug. 27, 1940 2,266,884 Martin Dec. 23, 1941 2,298,872 Dalkowitz Oct. 13, 1942 2,331,873 Thews Oct. 19, 1943 2,341,833 Voiz Feb. 15, 1944 2,462,625 Florman Feb. 22, 1949 2,494,464 Vivie et al Jan. 10, 1950 2,677,885 Chaun May 11, 1954 2,816,358 Vivie Dec. 17, 1957 2,824,367 McWilliams Feb. 25, 1958 FOREIGN PATENTS 232,705 Switzerland Mar. 10, 1944 234,183 Switzerland Dec. 16, 1944 550,903 Great Britain Ian. 29, 1943 1,034,511 Germany Oct. 1, 1957 1,188,529 France Mar. 16, 1959 

